1. Field of the Invention
The present invention relates generally to a QOS protection system. More particularly, the invention relates to a recovering method of a packet in a bi-directional real time television conference system, for recovering the packet from a failure, such as late arrival or so forth.
2. Description of the Related Art
In the recent years, demand for applications requiring real time transmission, such as a bi-directional real time television conference system, has been growing significantly. This means that systems requiring detection of xe2x80x9clate arrivalxe2x80x9d, xe2x80x9cpacket lossxe2x80x9d, xe2x80x9cpacket errorxe2x80x9d at a packet level, xe2x80x9cvariation of late arrivalxe2x80x9d and recovering from those failure.
Conventionally, as a recovering method from the failure, there has been an established method for detecting a failure, such as signal interruption or error in a section, a line or a bus with taking the resultant value as a trigger for switching.
Here, as a cause of xe2x80x9clate arrivalxe2x80x9d of the packet, it has been considered (1) a period required for transmission through all physical links and a period required in each node and (2) a period to be placed in waiting state upon congestion of the packet. (1) is determined in straightforward depending upon the network. On the other hand, (2) is a cause of xe2x80x9cvariation of late arrivalxe2x80x9d and is variable depending upon variation of congestion at each node.
On the other hand, as a cause of xe2x80x9cpacket lossxe2x80x9d is (1) xe2x80x9cpacket errorxe2x80x9d due to line error or so forth and error correction is not possible, or (2) disposal of an ATM (Asynchronous Transfer Mode) cell due to violation of UPC (Usage Parameter Control) or NPC (Network Parameter Control).
However, in connection with the packet delay or packet variation, there has not been developed or proposed a method to detect the packet delay or the variation of the delay for switching a current system and a reserved system with taking detection as trigger.
In the above-mentioned conventional recovering method for the packet from failure, at first, the detection of the packet delay and the variation of the delay period to take the detection as trigger for switching between the current system and the reserved system is not considered. Therefore, there is not such particular method effective for the packet delay and the variation of the packet delay, and thus can recover quality at the packet level. This problem is critical.
Namely, despite of the fact that it has been necessary to monitor arriving condition of the healthy packet for detecting xe2x80x9clate arrivalxe2x80x9d, xe2x80x9cpacket lossxe2x80x9d, xe2x80x9cpacket errorxe2x80x9d, xe2x80x9cvariation of late arrivalxe2x80x9d at packet level not causing complete failure, in addition to the failure of signal interruption, transmission error and so forth which has been monitored conventionally, to regard degradation of quality as failure to perform switching.
Therefore, the present invention has been worked out for solving the problem in the prior art set forth above. It is an object of the present invention to provide a QOS xe2x80x98Quality of Servicexe2x80x99 protection which monitors the arriving condition of packets for switching between a current system and a reserved system depending upon degradation of quality to guarantee QOS.
According to one aspect of the present invention, a QOS protection system in a redundant system including a current system and a reserved system for monitoring packet flow for detecting at least one defect information among section, line and path and recovering the defect, comprises:
detection means for monitoring the packet flow and detecting at least the quality of degradation of the packet flow; and
switching means for performing switching between the current system and the reserved system when the detection means detects degradation of quality.
The QOS protection system takes not only section or line, such as loss of signal and transmission but also defect information of path and xe2x80x9closs of packetxe2x80x9d or xe2x80x9cpacket errorxe2x80x9d or xe2x80x9clate arrivalxe2x80x9d or xe2x80x9cpacket variationxe2x80x9d as trigger for initiating operation of own system and whereby to trigger protection.
For application requiring real time transmission, not only defect, such as loss of signal, transmission error or so forth but also degradation of quality are monitored for switching the current system and the reserved system for guarantee QOS.
More particularly, in order to effect switching by detecting defect or degradation of input packet flow, the packet in the packet flow is input to a defect detection in a QOS protection function portion.
The defect detection portion includes the path defect detection portion for detecting defect in section, line or path and the packet defect detection portion for proving switching command for switching between the current system and the reserved system for the switching portion when defect of degradation is detected by these detection portions.
By this, since xe2x80x9clate arrivalxe2x80x9d, xe2x80x9closs of packetxe2x80x9d, xe2x80x9cpacket errorxe2x80x9d and xe2x80x9cpacket variationxe2x80x9d can be detected, it becomes possible to switch between the current system and the reserved system depending upon degradation of quality by monitoring the arriving condition of the packet to permit transmission with guarantee of QOS. This is quite effective for the application requiring real time transmission.